Self-started mode-locking with dispersion-imbalanced nonlinear amplifier loop

Self-started mode-locking in a polarization-maintaining figure-eight Er-doped fiber laser was demonstrated by optimizing the dispersion and the nonlinearity in the nonlinear amplifier loop mirror. Experimental results indicate that the build-up time of soliton pulse is directly linked to the available pump power and net dispersion. Three laser diodes, one in a linear loop and the others in a nonlinear loop, were applied to provide enough pump power for the start-up of the nonlinear evolution. As long as 8-min build-up time was observed as the net dispersion approaches to -0.115 and -0.043 ps², it dramatically decreased to approximately millisecond order of magnitude as the net dispersion was optimized to -0.062 ps². Stable single soliton could be obtained by reducing the hysteresis pump power.